Phenolic Tubes, high speeds

[jraice]

I am thinking about designing a 29mm minimum diameter phenolic rocket, conical cone, small sleek but effective fined rocket. It will hopely fly on an Ellis mountain H275. I have not simmed it yet but the H275 took my 2.5" diameter 1.5 pound rocket a little over mach so this 29mm rocket should go about 950-1050 MPH, it might even get 1100 MPH. Will public missiles phenlic tubing be able to take the speed, it will be motor mount tubing? Also do nose cones fit into motor mount tubing?

 

[RocketboyG80]

Are you sure you got mach 1 from an H motor in a 2.5" 1.5lb roc? Doesn't quite sound like enough power for something of that size and weight. Although it will certainly push a minimum diameter rocket to mach speeds. About phenolic tubing taking that kind of speed, I'd say you're pushing it's limits but it might be able to handle it. Most people will probably tell you that you should 'glass it though. Or you can go the easier route and buy some Hawk Mountain 29mm fiberglass tubing. And yes the PML 29mm resin nosecone fits PML 29mm phenolic tubing (they call it motor mount tubing, but that doesn't mean anything). Hawk and PML 29mm tubing have the exact same thickness so they are fully compatible if you decide to use fiberglass instead of phenolic tubing.

 

[North Star]

PML have a good website with all the info you'll need, the airframe FAQ is here

https://publicmissiles.com/images/PMLAirframesFAQ.pdf

It says their tubes under 2.6" dia. are OK for transonic speeds ,bigger than that it should be glassed. As its a minimum dia bird will you be glassing it anyway in order to keep the fins on ?

 

[jraice]

Well yes I would be glassing it but only the fin joints, not the entire body, either way this was just an idea, might not be a real project for awhile.

 

[Stymye]

I don't see the advantage of using phenolic for a body tube unless it's glassed..otherwise their are far better options.

phenolic alone has a certain brittle quality to it but add epoxy/glass and you have a very strong tube.and will get the full benefit of using phenolic in the first place.

phenolic tubing alone is like peanut butter and jelly.....without the bread.

 

[lalligood]

Originally posted by jraice
I am thinking about designing a 29mm minimum diameter phenolic rocket, conical cone, small sleek but effective fined rocket. It will hopely fly on an Ellis mountain H275. I have not simmed it yet but the H275 took my 2.5" diameter 1.5 pound rocket a little over mach so this 29mm rocket should go about 950-1050 MPH, it might even get 1100 MPH. Will public missiles phenlic tubing be able to take the speed, it will be motor mount tubing? Also do nose cones fit into motor mount tubing?

Just to clarify, are you wanting to build a 29mm minimum diameter rocket or a 2.5 diameter rocket with a 29mm MMT? They are definitely NOT the same thing.

If you want to build a 29mm minimum diameter rocket, believe it or not paper tubing (without fiberglassing) should be more than sufficient. Not Estes thin paper tubing but LOC or USR tubing should be more than enough to get the job done.

2.5" unglassed paper tubing should be sufficient for high velocity flights as well. I'd be surprised if an H (even a high thrust H) would break Mach at that diameter. A mid to high thrust I would do the trick if the rocket was built lightly though.

 

[DynaSoar]

Originally posted by jraice
I am thinking about designing a 29mm minimum diameter phenolic rocket, conical cone, small sleek but effective fined rocket. It will hopely fly on an Ellis mountain H275. I have not simmed it yet but the H275 took my 2.5" diameter 1.5 pound rocket a little over mach so this 29mm rocket should go about 950-1050 MPH, it might even get 1100 MPH. Will public missiles phenlic tubing be able to take the speed, it will be motor mount tubing? Also do nose cones fit into motor mount tubing?

Phenolic will, by PML's own FAQ, stand Mach+ stress at that small diameter. I've got one that's made of heavy wall motor mount cardboard tube, not even phenolic. No problem.

Motor mount tubing is the same as airframe tubing. 29mm = 1.1" in PML terms.

Consider using PML's conical urethane nose. Very nice. Yes, it'll fit.

Definitely strengthen the fin/body joints, since you'll be using surface mount fins by necessity. A strip of fiberglass cloth under the fillet is a common treatment. I used wood strips buried under the fillets.

Keep it down to around 12 ounces like mine, and you should be able to get over 1000 MPH on the H275. Good luck finding it after, it should top 7000' easy.

 

[lalligood]

I forgot to mention that a 29mm minimum diameter rocket with paper tubes & a balsa (yeah, you heard me right--balsa) nose cone can weigh less than 4oz. With a G80-10T, it should easily break Mach. FWIW, max altitude will be in the 3500-4000ft range.

HTH,

 

[jraice]

To clarify i want to make a 29mm rocket. I was saying I have built 2.5" rockets that broke mach with the H275.

 

[bobkrech]

While I don't have an .eng file for the EM275, the AT268R is pretty close and I can't get it to break Mach in a 2.6" rocket (VB Javelin 2.6) when simmed in Wrasp (M=0.85 and 3300 ft.), nor can I get a VB29 to break Mach on a G80 in Wrasp either (M=0.87 and 4700 ft.).

But a stock VB29 on an AT268R will easily break mach at M=1.68 and 7900 ft. when simmed in Wrasp. The VB29 was just about the fastest 29 mm bird available, but unfortunately VB went out of business about 2 years ago. It wasn't anything fancy, just a 3FNC with a plastic NC, cardboard airframe, and epoxied FG fins. You don't need anything more, but you probably should glass the fins to the airframe as per the PML Cirrus directions with this motor in a 29 mm airframe. If you are determined to get a bullet proof glass rocket, the Hawk Mountain Raptor is an excellent 29 mm FG kit that will hit M=1.18 and 8000 ft on an AT 268R.

The bottom line is the lighter you make it, the faster it will go.

Bob Krech

 

[xenon]

I think phenolic tubing should be fine at those speeds.
With 29mm, you should be getting very, very close to mach 2. I had a 35mm (bt-55) rocket on a H275 and it was supposed to get M1.75, although it shredded at about 900mph, it was moving dang fast. You should be okay though, just glass the fins on. Giant Leap phenolic would be a bit better, it seems more fexible and not quite as brittle.

What are you using for fins?